Hydrochloric Acid Storage — Tank, Resin & System Selection
Hydrochloric Acid Storage — Tank, Resin & System Selection
OEM-verified materials of construction for 37% muriatic hydrochloric acid storage in rotomolded polyethylene tanks.
Overview
Hydrochloric acid (HCl), sold commercially as muriatic acid at around 31% to 37% concentration, is one of the most aggressively corrosive mineral acids in common industrial use. It is consumed in metal pickling, pool and spa pH control, concrete etching, ore processing, and food-grade gelatin production. At 37% and ambient temperature HCl attacks most common tank metals (carbon steel, 316 stainless, aluminum) on contact. Properly specified polyethylene is the standard tank material for HCl service — but the gasket and bolting hardware determine whether the system holds.
Why HDLPE Only — No XLPE
Snyder Industries specifies linear polyethylene (HDLPE) for 37% HCl service at 1.9 ASTM specific gravity. Crosslinked polyethylene (XLPE) is not approved for this service: HCl fumes migrate into crosslink junctions and produce stress-cracking failures even when the liquid itself doesn't directly attack the resin. This is a documented OEM position, not a theoretical concern.
Gasket: Viton, Not EPDM
EPDM — the default gasket material for water and most benign chemistries — fails in HCl service. It swells, loses rebound, and eventually cracks. Viton (FKM) is required for any wetted gasket: the manway, bulkhead fittings, flanged connections, and pump gaskets. If you see an EPDM gasket on an HCl installation, plan to replace it on the next planned outage.
Bolt Material: Hastelloy
Snyder specifies Hastelloy (C-276 family) for HCl tank hardware. 316 stainless steel pits within weeks in HCl vapor service, even where the bolt head is not wetted. Titanium, which works for many other acids, is not recommended for HCl because chloride attack is cathodic. The Hastelloy spec is not optional — using 316SS will void the OEM service rating and create a known failure path.
Fitting Material: PVC
PVC bulkhead fittings and piping are used throughout HCl service. CPVC works too but is overkill for cold or ambient storage. For heated transfer (uncommon at 37%), step up to CPVC or PVDF. Do not use glass-filled nylon or polypropylene threaded fittings — HCl embrittles them.
System-of-Construction Table (Snyder Industries)
This is the exact specification Snyder Industries publishes for this chemistry. Every column is required — changing any of them voids the service rating.
| Concentration | Resin | Specific Gravity | Fitting | Gasket | Bolt |
|---|---|---|---|---|---|
| 37 | HDLPE | 1.9/ASTM | PVC | Viton | Hastelloy |
Concentration-Band Compatibility (Enduraplas / Equistar Data)
Polyethylene chemical resistance by concentration and service temperature. Satisfactory (S) = long-term service. Limited (O) = occasional only. Unsatisfactory (U) = do not use.
| Concentration | LDPE/MDPE @ 70°F | LDPE/MDPE @ 140°F | HDPE @ 70°F | HDPE @ 140°F |
|---|---|---|---|---|
| 10% | Satisfactory | Satisfactory | Satisfactory | Satisfactory |
| 30% | Satisfactory | Satisfactory | Satisfactory | Satisfactory |
| 35% | Satisfactory | Satisfactory | Satisfactory | Satisfactory |
| Conc. | Satisfactory | Satisfactory | Satisfactory | Satisfactory |
Frequently Asked Questions
- Can I store muriatic acid in a standard utility tank?
- No. Standard water tanks are spec'd at 1.5 ASTM SG. HCl at 37% weighs 1.19 SG so the tank wall is not the limit — but the fittings, gaskets, and bolting are. A tank rated for HCl service must have Viton gaskets, Hastelloy bolts, and PVC fittings as a complete system.
- Does the tank need secondary containment?
- Most state and local fire codes require secondary containment for HCl storage over 55 gallons. Double-wall tanks (DW in the Snyder catalog) satisfy this with factory-integrated secondary containment. If using a single-wall tank, expect to build a lined concrete berm or install a containment basin sized for 110% of tank volume.
- Will the tank discolor?
- Less than sulfuric. HCl service typically leaves a faint yellow tint on HDLPE over years of exposure. This is cosmetic; it does not indicate degradation.
- Can I use a delivery tote for long-term HCl storage?
- IBC totes are rated for transport, not indefinite storage. The gaskets and valves on a stock IBC are usually not Viton. For permanent installations order a vertical HDLPE tank specifically commissioned for HCl service.
Source Citations
- Snyder Industries — Chemical Resistance Recommendations (current edition)
- Enduraplas / Equistar Technical Tip — Chemical Resistance of Polyethylene (12-page reference)
Chemical-Service Tanks
These HDPE vertical chemical-storage tanks from Snyder Industries ship pre-engineered for industrial chemistry service at 1.9 ASTM design specific gravity. When you order for hydrochloric acid / muriatic service, our team verifies the full materials-of-construction stack (resin grade, fittings, gaskets, bolts) against the OEM recommendations above before shipment — no surprises at commissioning.
Need your state's septic or tank regulations?
Chemical service tanks are spec'd at the manufacturer level, but the installation still has to comply with your state and county rules — setbacks, containment, permitting, and in some states, construction-authorization review. Our State Regulation Guides cite actual statutes, not generic lore.